1. Field of the Invention
The present invention relates to methods and apparatus for cutting, welding, drilling or surface treating a workpiece using a laser.
2. Description of the Prior Art
At present such methods employ a lens or mirror system to focus the beam with the object of achieving a high energy intensity over a small area. A gas jet concentric with the laser beam has been found useful and an oxygen jet greatly increases the range of possible cutting speeds together with depths of penetration. The oxygen reacts with a metallic workpiece causing an enhanced energy flux. For non-metals an inert gas increases the cutting rate probably by blowing liquid material clear.
However, present cutting and welding speeds and the depths achieved are insufficient for the majority of applications. Recent studies using a 15-20 kW laser have resulted in performance figures well below those suggested by a linear extrapolation from low power work. This poor performance may be due to optical design, masking of the workpiece by the laser induced plasma (that is a cloud of vaporised particles some of which are electrically charged) or some other reasons. In any case it is primarily due to lack of energy reaching the workpiece and suggests that the way ahead for laser processes is not by way of higher laser powers.